The Historia Compostellana is primarily a narrative of the deeds of Diego Gelmírez. These deeds narrated encompass the period from 1100 to 1139, that is, the years during which Gelmírez was first bishop (1100-1120) and then archbishop of Compostela until his death (1120-1140). Because of the important role Diego Gelmírez played in the history of Galicia, these almost forty years could easily be referred to as "the times of Gelmírez". In the kingdom of Castilla-Le6n, these years coincide with the reigns of Alfonso VI (to 1109), of his daughter Urraca (1109-1126), and of Alfonso VII (from 1126).
The question of the authorship of the Historia Compostellana has been amply discussed, although all of the researchers who have dealt with this matter agree that it is evident that the authors of this work belong to the circle of persons close to Archbishop Gelmírez and are under his protection, as proven by the offices and missions which they receive from him. It seems fitting to speak of two fundamental authors (Nuño Alfonso and Gerald) and of two or three secondary authors (Hugo, Pedro, and, perhaps, a fifth author).
We are in the presence of a historical work which is contemporary to the events it narrates. We can contemplate the Historia Compostellana as a documentary source in itself, which has transmitted historical texts that would be unknown to us without its existence. The inclusion of documents of a diverse nature is one of the work's principal characteristics, and these documents make of this work a real diplomatic collection of inestimable value.
The edition that appears here is the first critical edition of the Historia Compostellana. The need for a critical edition of one of the fundamental sources of Spanish medieval history had been pointed out by several authors, but since Flórez’s publication of the text in 1765, it had not been reedited. The present edition attempts to improve on Flórez's edition by availing itself fundamentally of a detailed study of the codexes. The editor's intention is to present to both one and the other, philologists and historians, a reliable text, with the security of a critical apparatus.